It has conventionally been known that high-quality ashless coals are obtained by removing ash components, etc. from coals, and techniques for improving the yield of such ashless coals are being developed. As a method for obtaining an ashless coal from a coal, there is a method in which the components other than ash components and the like, which are soluble components, are extracted from a coal by dissolving them out in a solvent and the solvent is evaporated and separated from the solution which contains the soluble components dissolved therein. According to this method, the yield of ashless coal can be improved by heightening the coal extraction rate by dissolving soluble components of the coal in the solvent as much as possible.
For that purpose, for example, the method for producing an ashless coal described in Patent Document 1 employs 1-methylnaphthalene, which has an excellent affinity for coals, as the solvent in order to heighten the extraction rate. However, a solvent which brings about a higher coal extraction rate has been desired for further improving the yield of ashless coal.